 /*******************************************************************************
  * Copyright (c) 2006 IBM Corporation and others.
  * All rights reserved. This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License v1.0
  * which accompanies this distribution, and is available at
  * http://www.eclipse.org/legal/epl-v10.html
  *
  * Contributors:
  * IBM Corporation - initial API and implementation
  *******************************************************************************/
 package org.eclipse.core.resources.mapping;

 import java.util.ArrayList ;
 import java.util.List ;
 import org.eclipse.core.internal.resources.mapping.ChangeDescription;
 import org.eclipse.core.internal.resources.mapping.ResourceChangeDescriptionFactory;
 import org.eclipse.core.internal.utils.Messages;
 import org.eclipse.core.internal.utils.Policy;
 import org.eclipse.core.resources.*;
 import org.eclipse.core.runtime.*;
 import org.eclipse.osgi.util.NLS;

 /**
  * The resource change validator is used to validate that changes made to
  * resources will not adversely affect the models stored in those resources.
  * <p>
  * The validator is used by first creating a resource delta describing the
  * proposed changes. A delta can be generated using a {@link IResourceChangeDescriptionFactory}.
  * The change is then validated by calling the {@link #validateChange(IResourceDelta, IProgressMonitor)}
  * method. This example validates a change to a single file:
  * <code>
  * IFile file = ..;//some file that is going to be changed
  * ResourceChangeValidator validator = ResourceChangeValidator.getValidator();
  * IResourceChangeDescriptionFactory factory = validator.createDeltaFactory();
  * factory.change(file);
  * IResourceDelta delta = factory.getDelta();
  * IStatus result = validator.validateChange(delta, null);
  * </code>
  * If the result status does not have severity {@link IStatus#OK}, then
  * the changes may cause problems for models that are built on those
  * resources. In this case the user should be presented with the status message
  * to determine if they want to proceed with the modification.
  * </p>
  *
  * @since 3.2
  */
 public final class ResourceChangeValidator {

     private static ResourceChangeValidator instance;

     /**
      * Return the singleton change validator.
      * @return the singleton change validator
      */
     public static ResourceChangeValidator getValidator() {
         if (instance == null)
             instance = new ResourceChangeValidator();
         return instance;
     }

     /**
      * Singleton accessor method should be used instead.
      * @see #getValidator()
      */
     private ResourceChangeValidator() {
         super();
     }

     private IStatus combineResults(IStatus[] result) {
         List notOK = new ArrayList ();
         for (int i = 0; i < result.length; i++) {
             IStatus status = result[i];
             if (!status.isOK()) {
                 notOK.add(status);
             }
         }
         if (notOK.isEmpty()) {
             return Status.OK_STATUS;
         }
         if (notOK.size() == 1) {
             return (IStatus) notOK.get(0);
         }
         return new MultiStatus(ResourcesPlugin.PI_RESOURCES, 0, (IStatus[]) notOK.toArray(new IStatus[notOK.size()]), Messages.mapping_multiProblems, null);
     }

     /**
      * Return an empty change description factory that can be used to build a
      * proposed resource delta.
      * @return an empty change description factory that can be used to build a
      * proposed resource delta
      */
     public IResourceChangeDescriptionFactory createDeltaFactory() {
         return new ResourceChangeDescriptionFactory();
     }

     private ModelProvider[] getProviders(IResource[] resources) {
         IModelProviderDescriptor[] descriptors = ModelProvider.getModelProviderDescriptors();
         List result = new ArrayList ();
         for (int i = 0; i < descriptors.length; i++) {
             IModelProviderDescriptor descriptor = descriptors[i];
             try {
                 IResource[] matchingResources = descriptor.getMatchingResources(resources);
                 if (matchingResources.length > 0) {
                     result.add(descriptor.getModelProvider());
                 }
             } catch (CoreException e) {
                 Policy.log(e.getStatus().getSeverity(), NLS.bind("Could not instantiate provider {0}", descriptor.getId()), e); //$NON-NLS-1$
 }
         }
         return (ModelProvider[]) result.toArray(new ModelProvider[result.size()]);
     }

     /*
      * Get the roots of any changes.
      */
     private IResource[] getRootResources(IResourceDelta root) {
         final ChangeDescription changeDescription = new ChangeDescription();
         try {
             root.accept(new IResourceDeltaVisitor() {
                 public boolean visit(IResourceDelta delta) {
                     return changeDescription.recordChange(delta);
                 }
             });
         } catch (CoreException e) {
             // Shouldn't happen since the ProposedResourceDelta accept doesn't throw an
 // exception and our visitor doesn't either
 Policy.log(IStatus.ERROR, "Internal error", e); //$NON-NLS-1$
 }
         return changeDescription.getRootResources();
     }

     /**
      * Validate the proposed changes contained in the given delta
      * by consulting all model providers to determine if the changes
      * have any adverse side effects.
      * <p>
      * This method returns either a {@link ModelStatus}, or a {@link MultiStatus}
      * whose children are {@link ModelStatus}. In either case, the severity
      * of the status indicates the severity of the possible side-effects of
      * the operation. Any severity other than <code>OK</code> should be
      * shown to the user. The message should be a human readable message that
      * will allow the user to make a decision on whether to continue with the
      * operation. The model provider id should indicate which model is flagging the
      * the possible side effects.
      * </p>
      *
      * @param delta a delta tree containing the proposed changes
      * @return a status indicating any potential side effects
      * on models stored in the affected resources.
      */
     public IStatus validateChange(IResourceDelta delta, IProgressMonitor monitor) {
         monitor = Policy.monitorFor(monitor);
         try {
             IResource[] resources = getRootResources(delta);
             ModelProvider[] providers = getProviders(resources);
             if (providers.length == 0)
                 return Status.OK_STATUS;
             monitor.beginTask(Messages.mapping_validate, providers.length);
             IStatus[] result = new IStatus[providers.length];
             for (int i = 0; i < providers.length; i++)
                 result[i] = providers[i].validateChange(delta, Policy.subMonitorFor(monitor, 1));
             return combineResults(result);
         } finally {
             monitor.done();
         }
     }
 }

